I just recently modded my friend’s old iPod (she gave it to me because she had no use for it) with a 3000mAh battery and...

I would recommend buying a motherboard off of eBay or some other website where you can buy iPod parts. The charging port is attached to the motherboard itself so you will need to replace the entire motherboard or solder in a new charging connector.

While yes it might be possible that it is not meant to come off (I don’t think this model does) but I would recommend using Isopropyl Alcohol or some other adhesive remover.

I believe the issue with this specific iPod is that the 30-pin connector on the Logic Board is damaged. While yes, it may charge, it probably doesn’t have the ability to sync data. I would suggest finding a cheap one on eBay and then replacing it yourself. (It’s actually quite a fun process!).